From Edward Heath in the 1970s to Labour in the past decade, leaders have tried to resolve London’s aviation dilemma. Picture: Economist/CAA

AS AN opposition Tory leader anxious to throw off his party’s image as the home of rapacious Gradgrinds, David Cameron made an eye-catching pledge in October 2009. “The third runway at Heathrow is not going ahead, no ifs, no buts,” he declared, setting his party against Labour’s plans for airport expansion. Homeowners around London’s western fringe cheered.

The move enhanced Mr Cameron’s green credentials—a key part of his strategy to reposition the Conservative Party as more socially aware. It also boosted the Tories’ electoral prospects in marginal seats like Richmond Park and Brentford, which are already uncomfortably noisy (see map).

Alas, the days when making Conservatism sound nice was a priority are long gone. As politicians return to Westminster for a new term, the prime minister is focused on the stubbornly lagging economy, which is a drag on the coalition’s popularity and his own.

Backbenchers and businessfolk think they have a solution: grant the capital’s main airport room to grow so the country can attract more business from China and other emerging economies. Tim Yeo, Tory chairman of Parliament’s energy committee, has changed his mind to favour a new runway and is loudly urging Mr Cameron to do likewise. Powerful backers like Sir Michael Spencer, a City broker, also support a U-turn.